Beta-lactamases are a family of enzymes that hydrolyze beta-lactam rings, such as beta-lactam rings of beta-lactam antibiotic drugs. Beta-lactamases are found in gram positive and gram negative bacteria and are responsible for the antibiotic resistance of many bacterial strains.
Beta-lactamases can be classified on the basis of their primary structure into four molecular classes, namely classes A to D. Classes A, C and D have a serine residue at their active site and class B, or metallo-beta-lactamases, have zinc at their active site. Carbapenemases are a diverse group of beta-lactamases that include enzymes belonging to class A, B and D. Class A carbapenemases include KPC-1, KPC-2, KPC-3 and KPC-4. Class B carbapenemases include the IMP family, VIM family, GIM-1 and SPM-1 as well as others. Class D carbapenemases include OXA-23, OXA-24, OXA-25, OXA-26, OXA-27, OXA-40 and OXA-40 as well as others. AmpC beta-lactamases are class C enzymes and can be encoded by chromosomal genes or be plasmid-borne. AmpC beta-lactamases hydrolyze broad and extended-spectrum cephalosporins (i.e., cephamycins and oxyimino-beta-lactams). Extended-spectrum beta-lactamases (ESBLs) are beta-lactamases that hydrolyze cephalosporins with an oxyimino chain. ESBLs include the TEM family, SHV family as well as others, and CTX-M family, which are class A enzymes. Original-spectrum beta-lactamases (OSBLs) include class A enzymes.
The spread of beta-lactamases between bacteria has increased the resistance of bacteria to beta-lactam drugs. The administration of beta-lactam drugs to patients with bacteria resistant to those drugs selects for those bacteria and leads to an increase in the transmission of beta-lactamases. Thus, there is a need to rapidly detect bacteria expressing specific beta-lactamases so that an appropriate therapeutic regimen is selected for a given patient and the likelihood of the spread of resistant bacteria is reduced.